Control system



Oei. 14, 1952 w. H. HAILEY 2,613,878

CONTROL SYSTEM Filed Feb. 28, 1949 IN VEN TOR. M//fmy /z f//ye/ Patented Oct. 14, 1952 CONTROL SYSTEM William H. Hailey, Kansas City, Mo., assignor to Schreiber Mills, Inc., St. Joseph, Mo., a corporation of Missouri Application February 28, i949, Serial No. 78,772

6 Claims.

This invention relates to electro-mechanical control means capable when placed in use for shifting any member to which the same is connected through a given path of travel in response to flow of power through an electric circuit and in direct proportion thereto.

The invention forming the subject matter hereof has been developed primarily for use in feed mills for controlling the flow of grain or the like to a feed grinder operable to vary said flow in direct proportion to the load requirements of the grinder itself as determined by the character of the feed.

For purposes of clarity, the control system hereof will be hereinafter fully described in connection with a feed grinder, but it will become readily apparent upon an understanding of the operation of the system that the same is capable of many and varied uses differing from that speciiically set forth.

It is common knowledge by millers and others generally that a distinct problem exists in the handling of grain and other products, particularly during grinding operations, because of the fact that such grain will vary in moisture content and in inherent characteristics thereof depending upon the source, quality, type and condition of the grain itself.

Accordingly, when such grain is fed into a grinder at a constant speed, the requirements of the grinder will constantly vary, resulting in a wide range of load requirements upon the prime mover of the grinder and an over-all loss in speed and efficiency with respect to a given operation, as well as an appreciable increase in operating costs.

It is appreciated that means have heretofore been provided to automatically render feeding systems inoperable upon an overloading of the grinder itself; and, further, structures have been produced in the form of reversing mechanisms to effect at least a certain degree of control. However, as far as I am aware, no inexpensive, relatively simple means has heretofore been disclosed operable in effecting control pf grain feeding mechanisms and capable of assuring operation of the grinder motor at full capacity at all times, irrespective of the condition of the grain being ground.

It is the most important object of the present invention, therefore, to provide a control system including a differential mechanism having a main rotatable driven member operably connected with structure for controlling the speed of iiow of grain to a feed grinder, the said member having torque applied thereto such that its speed of rotation is in direct proportion to the departure from a predetermined load of the prime mover of the grinder upon its electric circuit.

Another important object of the present invention is to provide a control system as above set forth having a differential gearing mechanism of conventional character, having a pair of shafts and a driven member, the shafts each being provided with a motor and the relative speeds of the motors being controlled by a transformer coupling the one of said motors with an electric circuit, all to the end that torque is applied to the driven member such that its speed of rotation is in direct proportion to the departure from a predetermined power ow through said circuit.

Additional objects will be made clear or become apparent as the following specification progresses, reference being had to the accompanying drawing, wherein:

The single figure is a diagrammatical view of an embodiment of my present invention.

There is shown in the drawing, for purposes of illustration, a conventional feed grinder I0 having a laterally extending trough I2 for receiving feed to be ground thereby and directing the same into the grinding mechanism by force of gravity.

Feed grinder I0 is driven by a three phase induction electric motor I4 through the medium of a belt or the like I6, trained about pulleys I8 and I 9 on grinder I0 and motor I4 respectively.

The grain to be ground is usually contained in an overhead bin 2D provided with means for regulating the flow of such grain by force of gravity into the receiving trough I2 of grinder I0. In the instance shown, the bin or hopper 20 is provided with an open bottom covered by a rotatable disc 22.

A bevel gear 24 is secured to the lowermost end of a shaft 26 for disc 22, which shaft 26 is journaled in frame member 28. Continuous rotation of disc 22 is accomplished through use of an ,electric motor or the like 30 having a bevel gear 32 on its drive shaft that is in mesh with the bevel gear 24 of disc 22. The flow of grain from hopper 20 to the rotating disc 22 is controlled through the medium of a vertically slidable gate 34 mounted within spaced apart guides 36 and covering an opening (not shown) in one side of the hopper 20 when gate 34 is at the lowermost end of its path of travel, as illustrated in the drawing.

An elongated rack 38 is connected to and extends upwardly from the uppermost marginal gate 34, said rack 3B having a gear 40 in mesh therewith. Gear 4D is connected to one end of a shaft 42 mounted in bearings 44 on hopper 20 and is provided with a sprocket wheel 46 on that end thereof opposite to gear 40. A second sprocket wheel 48 is journaled in a bearing 58 on hopper and the two sprocket wheels 46 and 48 are interconnected by an endless chain 52.

The structure forming the subject matter of the present invention and operable to control the vertical reciprocable movement of the gate 34 in direct proportion to a departure from a predetermined load upon motor I4 includes a conventional differential gear mechanism broadly designated by the numeral 54. The precise formation of the differential mechanism 54 is of no particular importance to this invention and, since the same is of conventional character, details of construction thereof have not been illustrated.

Such mechanism, as is well known, includes an arrangement of gears formed in such manner as to present an epicyclic train for connecting apair of shafts 5S and 58 that are disposed in direct alignment as illustrated in the drawing. Such arrangement permits the shafts to revolve at different relativespeeds. Such differential mechanisms, also, include a rotatable driven member 68 which, in the present instance, is connected directly to the sprocket wheel 43.

A split phase constant speed electric motor 62 has its drive shaft connected directly to the shaft 56 in any suitable manner, or if desired, the snai t 56 may constitute the drive shaft of motor 62 and be formed to extend into the housing for the differential mechanism 54 and for connec" tion with the train of gears encased therein,

A variable speed shunt-wound D. electric motor 64 has its drive shaft operably connected directly to the shaft 58 of differential mechanism 54. A transformer 83 is provided with a primary winding 68 that is connected in series with one l of the supply lines IG for supplying electric power to the motor I4 that drives the grinder I0. Transformer 55 is especially chosen to have the characteristic that is secondary Voltage is proportional to its primary current. The armature of motor 64 is connected to a secondary winding 'I2 of transformer 66 through a bridge-type rectifier '14. Field winding IG of motor 64 is joined to a source of alternating current through a bridgetype rectifier i8. A pair of lead lines 88 and 82 are connected with such source or alternating current (not shown) and these lines 88 and 82 are joined to rectifier 'i8 through the medium of wires 84 and 8S. The wires connecting bridge rectifier 18 with the winding 'r6 of motor 84- are designated by the numerals 83 and 8G. Constant speed motor 62, also, derives its power through direct connection with lines 80 and 82.

It is obvious that the load upon the grinding system above set forth is indicated by the current drawn by motor I4 which, in turn, is determined by the position of gate 84 and the characteristics of the grain being ground by grinder IIJ. The system operates to maintain such load near a constant value when a change occurs in such characteristics of the grain through regulation of the position of gate 34 with respect to the opening in hopper which it covers. Through this system, the rate of change in the position of gate 34 is proportional to the deviation of the current drawn by motor I4 from such constant and predetermined value. Obviously, the speed of motor 54 is proportional to the electric voltage supplied to its armature and, accordingly, proportional to the current drawn by motor I4.

As above set forth, the differential mechanism 54 is so formed that the speed of rotatable member 60 is proportional to the difference in speeds between motors 62 and 64. It follows, therefore, that the speed of rotation of driving member is directly proportional to the difference between the current drawn by motor I4 at any given moment and a predetermined constant. Furthermore, mechanical connection between driving member 60 and gate 34 is so formed that the rate of change in the positioning of gate 34 is proportional to the output speed of differential mechanism 54,

Transformer is so constructed that motors 62 and 64 operate at the same speed when the current drawn by motor I4 is at the desired, predetermined value. Accordingly, when motor I4 is forced to draw more current in excess of the chosen value, more current flows through primary 68 of transformer 66 and, consequently, the voltage across secondary I2 of transformer 66 is increased. Thus, variable speed motor 64 will operate at a speed greater than the constant speed of rotation of motor 62. This will cause the normally stationary driving member to commence rotating in a direction to move the gate 34 toward a closed position. As gate 34 so moves, a lesser amount of grain will be fed to grinder I0, reducing the requirements of motor I4 and thereby automatically causing motor I4 to operate at the aforesaid chosen value.

Conversely, when motor I4 draws less current, variable speed motor 64 will operate at a speed that is less than the constant speed of motor 62, causing rotation of the driving member 60 in a direction to move gate 34 toward the fully opened position; and such movement of gate 34 will continue until motor I4 again draws the predetermined amount of current through primary 68 of transformer 66.

Summarizing, therefore, it is seen that with the proper choosing of the speed of .rotation of motor 62 to correspond with the desired normal current drawn by motor 54, as well as the mechanical interconnection between rotating member 60 and gate 34, grain will be delivered to the grinder I9 at a rate depending upon the characteristics of the grain, so as to maintain a uniform load upon motor I4.

It is apparent that the entire system and more particularly the structure which it controls is capable of many changes and modifications. It is within the broad concepts of this invention that the rotating member 60 of differential mechanism 54 may be connected directly to virtually any structure that is desired to be controlled in accordance with the load requirements of a motor I4.

It is obvious that an A, C. motor could be used for motor 64, thereby eliminating the necessity of rectifying bridges 74 and '18. However, since the speed of rotation or the type of A. C. motor necessary for this use is proportional to the load that is applied thereto, sensitivity of the system would be appreciably decreased by use of such motor.

Manifestly, therefore, those changes and modiications as fairly come Within the scope of this invention, as defined by the appended claims, are contemplated hereby.

Eaving thus described the invention, what I claim as new and desire to secure by Letters Patent is:

. l' fA Contll system comprising a main electric circuit; a differential gearing mechanism having a pair of rotatable shafts and a rotatable driven member; a constant speed electric motor operably connected with one of said shafts; a variable speed electric motor operably connected with the other shaft; an electric circuit for each motor respectively; and means coupling said main circuit with the electric circuit of said variable speed motor for controlling the torque of said member in response to power flow changes in said main circuit, said means including a transformer having a primary winding and a secondary winding in series with said main circuit and the electric circuit of said variable speed motor respectively.

2. A control system comprising a main electric circuit; a differential gearing mechanism having a pair of rotatable shafts and a rotatable driven member; means operably connected with one of said shafts for rotating the same at a constant speed; a variable speed electric motor operably connected with the other shaft; an electric circuit for said motor; and means coupling said main circuit with the electric circuit of said variable speed motor for controlling the torque of said member in response to power flow changes in said main circuit, said means including a transformer having a primary winding and a secondary Winding in series with said main circuit and the electric circuit of said variable speed motor respectively.

3. A control system comprising a prime mover; a main electric circuit for said prime mover; a differential gearing mechanism having a pair of rotatable shafts and a rotatable driven member; means operably connected with one of said shafts for rotating the same at a constant speed; a variable speed electric motor operably connected with the other shaf t an electric circuit for said motor; and means coupling said main circuit with the electric circuit of said variable speed motor for controlling the torque of said member in response to power flow changes in said main circuit, i

said means including a transformer having a primary winding and a secondary winding in series with said electric circuit for the prime mover and the electric circuit for the variable speed motor respectively.

4. In material handling structure, apparatus for receiving material and adapted to change the condition thereof by application of mechanical force directly thereto; mechanism for regulating the flow of the material to said apparatus; and a control system comprising an electric prime mover for said apparatus; a main electric circuit for said prime mover; a differentiating gearing mechanism having a pair of rotatable shafts and a rotatable drive member entirely separate from said apparatus and said material and operably coupled with said mechanism; means operably connected with one of said shafts for rotating the same at a constant speed; a variable speed electric motor operably connected with the other shaft; an electric circuit for said motor; and means coupling said main circuit with the electric circuit of said variable speed motor for controlling the speed and direction of rotation of said member in response to changes in power flow in said main circuit as occasioned by variances in mechanical force necessary to change said material and therefore variances in loads on said prime mover.

5. In structure for handling granular material, apparatus for receiving said material and adapted to change the condition thereof by application of mechanical force directly thereto; and a control system comprising a primary electric motor for said apparatus; a main electric circuit for said motor; a differential gearing mechanism having a pair of rotatable shafts and a rotatable drive member entirely separate from said apparatus; valving structure having parts operably coupled with said drive member for controlling gravitational flow of material to said apparatus; means operably connected With one of said shafts for rotating the same at a constant speed; a variable speed electric motor operably connected with the other shaft; an electric` circuit for said variable speed motor; and means coupling said main circuit with the electric circuit of said variable speed motor for controlling the speed and direction of rotation of said member in response to changes in power flow in said main circuit as occasioned by variances in loads on said primary motor, in turn determined by variances in power requirements of said apparatus in handling granular material emanating from said structure.

6. A control system comprising a feed grinder; an electric prime mover for said grinder; a main electric circuit for said prime mover; a differential gearing mechanism having a pair of rotatable shafts and a rotatable drive member; structure having a valve operably coupled with said member for controlling ow of feed to said grinder; means operably connected with one of said shafts for rotating the same at a constant speed; a variable speed electric motor operably connected with the other shaft; an electric circuit for said motor; and means coupling said main circuit with the electric circuit of said variable speed motor for controlling the speed and direction of rotation of said member in direct proportion to changes in power flow in said main circuit as occasioned by variances in loads on said prime mover in turn determined by variances in power requirements of said grinder in grinding feed emanating from said structures.

WILLIAM H. HAILEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,221,391 Thullen Apr. 3, 1917 1,514,591 Symser Nov. 4, 1924 1,846,923 Thompson et al Feb. 23, 1932 2,235,928 Hardinge Mar. 25, 1941 

